Question

The pka of the α-carboxyl group of glutamine is 2.17, and the pka of its α-amino group is 9.13. calculate the average net charge on glutamine if it is in a solution that has a ph of 8.20. if the charge is positive, do not enter a \" \" sign.

Answer 1

I think u add the numbers and get the total and divide by the set of numbers to get the average.

Answer 2

-0.1051

Step-by-step explanation:

First, we need to find the degree of dissociation (α) of each of the groups using the Handerson-Halsebach equation:

pH = pKa + log (α/1-α)

log (α/1-α) = pH - pKa

log (1-α/α) = pKa - pH

1-α/α =
`10^(pKa - pH)`

1-α =
`10^(pKa - pH)`*α

α =
`(1)/(10^(pKa-pH) +1)`

So, fo the α-carboxyl group:

α =
`(1)/(10^(-6.03) +1)`

α = 1.0000

And for the α-amino group

α =
`(1)/(10^(0.93) +1)`

α = 0.1051

In the ionization, the α-carboxyl group goes from neutral to a negative ion with charge -1, and the α-amino group goes from a positive ion with charge +1 to a neutral compound. So, the net charge is how many ions are presented multiplied by the charge.

For the first one, the value of α is the value of ions, but for the second, α represents the neutral, so the ions are 1-α:

-1*(1.000) + (+1)*(1-0.1051) = -0.1051